This invention relates to the continuous treatment in a gaseous atmosphere secluded from the ambient atmosphere of heavy or large objects, such as coils of strip material, and to apparatus and process advantageous for such treatment, as well as for other purposes.
While the invention in certain aspects is applicable to the continuous treatment of other types of heavy or large objects, it provides particular important advantages in the treatment of coils of strip metal, and particularly open coils of strip metal, and therefore will be described hereinafter primarily in connection with heat treatment of such coils.
In the open coil heat treatment of strip metal, a tight wound coil of strip metal is first recoiled into an open coil in which the spiral convolutions of the strip metal in the coil are spaced apart. While such an open coil is supported with its axis vertical on a base structure, a suitable heated treating gas is caused to flow through the spaces between the convolutions of the coil to contact both sides of the metal strip and thus rapidly and effectively treat the metal.
In heat treatment such as annealing, the steel strip in an open coil may be heated to as high as 1750.degree. F. by passing a suitable heated gas through the spaces between the convolutions of the coil. Other open coil treatments may involve modifying the chemical composition of the metal strip. For example, the carbon content of steel strip may be modified by the use of a suitable gas. Furthermore, treatments may involve oxidation, bright annealing, gas alloying, and treatments involving the application to the surfaces of the strip metal of materials that will react with constituents of the metal and treatment of such surfaces by passing a suitably heated gas between the spaced strip convolutions.
Heretofore, the heat treatment of such an open coil has been often effected in a bell type furnace such as an individual bell type furnace, or by apparatus embodying a plurality of furnaces through which the coils are inserted from a side in an automated apparatus. It is also known to heat treat open coils in a furnace in which the coils are supported on a hearth that rotates about a vertical axis that passes gases between the convolutions of each coil in a plurality of segregated stations.
Although the heat treatment of open coils are set forth above has proven to be a great improvement over the heat treatment of tight wound coils, the above described prior types of apparatus do not provide as many advantages as are deemed desirable. Thus, the individual bell type apparatus requires considerable time for operation due to the necessity of fixing the coil on a suitable support, placing an inner cover over the coil, then placing the bell over the inner cover, heat treating the coil, and then removing the bell and inner cover. The second and third types of apparatus described above, although capable of providing considerable improvements in speed and efficiency of operation over the individual bell apparatus, either require considerable floor space or capital investment, or do not have as high a production capacity as is made possible by the present invention.